Synthesis and spectroscopic properties of porphyrin-(thia)calix[4]arene conjugates

Calix[4]arene diacetate and tetraacetate together with their tetrathia-analogs served as starting compounds for the synthesis of novel porphyrin-calixarene conjugates. The introduction of monoaminotetraphenylporphyrin gave corresponding calixarene derivatives, bearing two or four porphyrin units on the lower calixarene rim. These compounds, immobilized in the cone conformation, possess interesting photophysical properties. The absorption and fluorescence emission spectra of the synthesized diporphyrins and tetraporphyrins reveal exciton coupling between the porphyrin units. The flexibility of the amidic bridges accounts for tuning of the degree of porphyrin coupling by the solvent polarity.